Nitrile polymer vulcanizate and process for the production thereof

ABSTRACT

A nitrite polymer vulcanizate having improved hot air aging characteristics is described. The nitrite polymer vulcanizate may be produced admixing a composition comprising: (i) a nitrite polymer; (ii) a filler; (iii) an additive selected from the group comprising: a strong base, a salt of a strong base and a weak acid, a salt of a weak acid, a carbodiimide, a polycarbodiimide and mixtures thereof; and (iv) a vulcanization system. A vulcanizable composition useful for producing such a vulcanizate and a method for improving the hot air aging characteristics of a nitrite polymer are also described.

FIELD OF THE INVENTION

The present invention relates to an improved nitrile polymer vulcanizateand to a process for the production thereof. More particularly, in oneof its aspects, the present invention relates to nitrile polymervulcanizates having improved hot air aging characteristics. In anotherof its aspects, the present invention relates to a vulcanizablecomposition useful to produce such vulcanizates. In yet another of itsaspects, the present invention relates to a method for improving the hotair aging characteristics of a nitrile polymer vulcanizate.

BACKGROUND OF THE INVENTION

The effects of oxidizing conditions on vulcanizates obtained frompolymers having carbon—carbon double bond unsaturation have long been aproblem, particularly in applications where the vulcanizates are exposedto elevated temperatures for extended periods of time. A variety ofapproaches have been developed in the art in an attempt to solve thisproblem.

It is known that the carbon—carbon double bonds of such polymersactivate the vulcanizate to oxidative attack. One solution to theproblem of oxidative attack is to use polymers with few or nocarbon—carbon double bonds. Examples of such polymers include butylrubber (copolymers of isobutylene and isoprene) which typically containfrom about 0.5 to about 3.0 mole percent of carbon—carbon double bondunsaturation, and ethylene-propylene copolymers which contain no suchunsaturation.

Certain applications, such as the various hoses and seals in the enginecompartment of automobiles, require vulcanized polymers with acombination of oil resistance, and resistance to oxidative attack in airat elevated temperatures for extended periods of time. Vulcanizates ofcopolymers of conjugated dienes and α,β-unsaturated nitrites, such asacrylonitrile-butadiene copolymer, commonly known as nitrile rubber orNBR, are well known for their oil resistance. However, they containcarbon—carbon double bond unsaturation and therefore are susceptible tooxidative attack unless subjected to special compounding procedures forthe production of oxidation resistant vulcanizates.

In order to reduce the amount of carbon—carbon double bond unsaturationin NBR and yet retain the copolymer's oil resistance which is thought tobe provided by the nitrile functional groups in the copolymer, methodshave been developed to selectively hydrogenate the carbon—carbon doublebond unsaturation of NBR without hydrogenating the nitrile groups toproduce hydrogenated NBR or HNBR. See for example, British patent1,558,491, the contents of which are hereby incorporated by reference.

While the development of HNBR has been a significant advance in the art,there is still room for improvement. Specifically, there is a continuingneed to develop nitrile polymer vulcanizates which are characterized byimproved physical properties such as hot air aging and the like.

SUMMARY OF THE INVENTION

It is an object of the present invention to obviate or mitigate at leastone of the above-mentioned disadvantages of the prior art.

It is another object of the present invention to provide a novel nitrilepolymer vulcanizate.

It is yet another object of the present invention to provide a novelprocess for producing a nitrile polymer vulcanizate.

It is yet another object of the present invention to provide a novelvulcanizable composition for producing a nitrile polmer vulcanizate.

It is yet another object of the present invention to provide a novelmethod for improving the hot air aging characteristics of a nitrilepolymer vulcanizate.

Accordingly, in one of its aspects, the present invention provides anitrile polymer vulcanizate produced by vulcanizing a compositioncomprising:

(i) a nitrile polymer;

(ii) a filler;

(iii) an additive selected from the group comprising: a strong base, asalt of strong base and a weak acid, a salt of a weak acid, acarbodiimide, a polycarbodiimide and mixtures thereof; and

(iv) a vulcanization system.

In another of its aspects, the present invention provides a process forproducing a nitrile polymer vulcanizate comprising the step of admixinga polymer composition comprising:

(i) a nitrile polymer;

(ii) a filler;

(iii) an additive selected from the group comprising: a strong base, asalt of strong base and a weak acid, a salt of a weak acid, acarbodiimide, a polycarbodiimide and mixtures thereof, and

(iv) a vulcanization system.

In yet another of its aspects, the present invention provides avulcanizable composition comprising:

(i) a nitrile polymer;

(ii) a filler;

(iii) an additive selected from the group comprising: a strong base, asalt of strong base and a weak acid, a salt of a weak acid, acarbodiimide, a polycarbodiimide and mixtures thereof; and

(iv) a vulcanization system.

In yet another of its aspects, the present invention provides a methodfor improving the hot air aging characteristics of a nitrile polymercomprising the step of admixing a nitrile polymer with an additiveselected from the group comprising: a strong base, a salt of a strongbase and a weak acid, a salt of a weak acid, a carbodiimide, apolycarbodiimide and mixtures thereof.

In yet another of its aspects, the present invention provides ahydrogenated nitrile polymer vulcanizate having a hot air aging time toreach 100% elongation at break of at least about 200 hours when measuredpursuant to ASTM-D573-88 at 150° C., the vulcanizate derived from asulfur-based vulcanization system.

Thus, it has been discovered that incorporation of a particular additivein a nitrile polymer vulcanizate results in a surprising and unexpectedimprovement in the hot air aging characteristics of the vulcanizate(i.e., an improvement in the resistance to oxidative attack in air atelevated temperature aging under oxidizing conditions). The improvementin the hot air aging characteristics of the vulcanizate can manifestitself in a number of ways, including (by way of example only) anincrease in: (i) the period of time needed for the vulcanizate to reach100% elongation at break at 150° C.; and (ii) the maximum servicetemperature to which the vulcanizate can be exposed for a specifiedperiod of time before reaching 100% elongation at break, when comparedto a vulcanizate made without the additive. The present vulcanizates mayalso be characterized by improvement (i.e., in comparison to avulcanizate produced without the additive) in one or more of thefollowing properties: aged hot fluid aging, aged compression set, ageddynamic elastic modulus (E′), aged dynamic viscous modulus (E″), agedstatic modulus, aged low temperature properties and aged hardness.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described with reference tothe accompanying drawings, in which:

FIGS. 1-5 illustrate comparative hot air aging characteristics betweennitrile polymer vulcanizates of the invention and conventional nitrilepolymer vulcanizates.

DETAILED DESCRIPTION OF THE INVENTION

Thus, various aspects of the present application relate to a compositioncomprising:

(i) a nitrile polymer;

(ii) a filler;

(iii) an additive selected from the group comprising: a strong base, asalt of strong base and a weak acid, a salt of a weak acid, acarbodiimide, a polycarbodiimide and mixtures thereof, and

(iv) a vulcanization system.

Components (i), (ii), (iii) and (iv) may be added independently of oneanother or in one or more sub-combinations thereof.

As used throughout this specification, the term “nitrile polymer” isintended to have a broad meaning and is meant to encompass a copolymerof a conjugated diene and an unsaturated nitrile.

The conjugated diene may be a C₄-C₆ conjugated diene. Non-limitingexamples of suitable such conjugated dienes may be selected from thegroup comprising butadiene, isoprene, piperylene, 2,3-dimethyl butadieneand mixtures thereof. The preferred C₄-C₆ conjugated diene may beselected from the group comprising butadiene, isoprene and mixturesthereof. The most preferred C₄-C₆ conjugated diene is butadiene.

The unsaturated nitrile may be a C₃-C₅ α,β-unsaturated nitrile.Non-limiting examples of suitable such C₃-C₅ α,β-unsaturated nitritesmay be selected from the group comprising acrylonitrile,methacrylonitrile, ethacyrlonitrile and mixtures thereof. The mostpreferred C₃-C₅ α,β-unsaturated nitrile is acrylonitrile.

Preferably, the copolymer comprises from about 40 to about 85 weightpercent of the copolymer of bound conjugated diene and from about 15 toabout 60 weight percent of the copolymer of bound unsaturated nitrile.More preferably, the copolymer comprises from about 60 to about 75weight percent of the copolymer of bound conjugated diene and from about25 to about 40 weight percent of the copolymer of bound unsaturatednitrile. Most preferably, the copolymer comprises from about 60 to about70 weight percent of the copolymer of bound conjugated diene and fromabout 30 to about 40 weight percent of the copolymer of boundunsaturated nitrile.

Optionally, the copolymer may further comprise a bound unsaturatedcarboxylic acid. Non-limiting examples of suitable such boundunsaturated carboxylic acids may be selected from the group comprisingfumaric acid, maleic acid, acrylic acid, methacrylic acid and mixturesthereof. The bound unsaturated carboxylic acid may be present in anamount of from about 1 to about 10 weight percent of the copolymer, withthis amount displacing a corresponding amount of the conjugateddiolefin.

Further, a third monomer may be used in production of the nitrilepolymer. Preferably, the third monomer is an unsaturated mono- ordi-carboxylic acid or derivative thereof (e.g., esters, amides and thelike).

While the invention may be used with fully or partially unsaturatednitrile polymers, a particularly preferred group of nitrile polymersuseful in the production of the present vulcanizate are hydrogenated orpartially hydrogenated nitrile polymers (also known in the art as HNBR).Preferably, the copolymer is hydrogenated and comprises a residualcarbon—carbon double bond unsaturation of less than about 30, morepreferably from about 30 to about 0.05 mole percent, even morepreferably from about 15 to about 0.05 mole percent, even morepreferably from about 10.0 to about 0.05 mole percent, even morepreferably from about 7.0 to about 0.05 mole percent, most preferablyfrom about 5.5 to about 0.05 mole percent.

The vulcanizable polymer composition preferably further comprises afiller. The nature of the filler is not particularly restricted and thechoice of suitable fillers is within the purview of a person skilled inthe art. Non-limiting examples of suitable fillers include carbon black(e.g., FEF, MT, GPF and SRF), clays, titanium dioxide, silica fillers(with or without unsaturated silanes) and the like. The amount of filleris conventional. Preferably, the filler is present in an amount in therange of from about 20 to about 130 parts by weight per hundred parts byweight of the nitrile polymer. More preferably, the filler is present inan amount in the range of from about 20 to about 100 parts by weight perhundred parts by weight of the nitrile polymer. Most preferably, thefiller is present in an amount in the range of from about 40 to about 80parts by weight per hundred parts by weight of the nitrile polymer.

The vulcanizable polymer composition further comprises an additiveselected from the group comprising: a strong base, a salt of strong baseand a weak acid, a salt of a weak acid, a polycarbodiimide, acarbodiimide and mixtures thereof. Non-limiting examples of strong basesuseful in the present vulcanizate may be inorganic bases selected fromthe group comprising sodium hydroxide, potassium hydroxide, calciumoxide and the like. Preferably, the salt has a pk_(a) of at least about9.0, more preferably at least about 10.0, most preferably in the rangeof from about 10.0 to about 14.0. A preferred group of additivescomprises a Group I metal (e.g., sodium, potassium, etc.) salt of a weakacid (e.g., carbonic acid, phosphonic acid, boric acid, C₁-C₃₀ fattyacids and the like.) Non-limiting examples of salts useful in thepresent vulcanizate may be selected from the group comprising sodiumcarbonate, sodium acetate, sodium phosphate, potassium carbonate, sodiumstearate, sodium EDTA and mixtures thereof. The most preferred salt issodium carbonate.

The additive is present in an amount of from about 0.5 to about 30 partsby weight per hundred parts by weight of nitrile polymer, morepreferably from about 1.0 to about 10.0 parts by weight per hundredparts by weight of nitrile polymer, most preferably from about 2.0 toabout 8.0 parts by weight per hundred parts by weight of nitrilepolymer.

The vulcanization system used in producing the present nitrile polymervulcanizate is conventional and the choice thereof is within the purviewof a person skilled in the art.

In one embodiment, the vulcanization system used in the presentinvention comprises an organic peroxide (e.g., dicumyl peroxide,2,2′-bis(tert-butylperoxy diisopropylbenzene and the like).

In another embodiment, the vulcanization system used in the presentinvention comprises sulfur or a conventional sulfur-containingvulcanization product such as Vulkacit™ DM/C (benzothiazyl disulfide),Vulkacit™ Thiuram MS/C (tetramethyl thiuram monosulfide), Vulkacit™Thiuram/C (tetramethyl thiuram disulfide), mixtures thereof and thelike. Preferably, such sulfur-based vulcanization systems furthercomprise a peroxide such as zinc peroxide.

In yet another embodiment, the vulcanization system used in the presentinvention comprises a reactive phenol-formaldehyde resin and a Lewisacid activator. It is known to those skilled in the art that a reactivephenol-formaldehyde resins may be prepared by reacting apara-substituted phenol with a molar excess of formaldehyde—see, forexample, U.S. Pat. No. 2,726,224, the contents of which are herebyincorporated by reference. The use of such phenol-formaldehyde resins invulcanization systems for butyl rubber is well known.

The vulcanization system used in the present process preferably containsat least about 3 parts by weight reactive phenol-formaldehyde resin perhundred parts by weight nitrile polymer. It is especially preferred touse from about 8 to about 16 parts by weight of the reactivephenol-formaldehyde resin per hundred parts by weight polymer. If morethan about 16 parts by weight of the resin per hundred parts of nitrilepolymer are employed, the entire composition tends to become resinous,and hence such high levels of resin are generally undesirable.

The Lewis acid activator may be present as a separate component such asstannous chloride (SnCl₂) or poly(chlorobutadiene). Alternatively, theLewis acid activator may be present within the structure of the resinitself—for example, bromomethylated alkyl phenol-formaldehyde resin(which may be prepared by replacing some of the hydroxyl groups of themethylol group of the resin discussed above with bromine). The use ofsuch halogenated resins in vulcanization systems for butyl rubber iswell known to those skilled in the art.

In the present process, the nitrile polymer, the filler, the additiveand the vulcanization system may be admixed in any conventional mannerknown to the art. For example, this polymer composition may be admixedon a two-roll rubber mill or an internal mixer. The preferredhydrogenated nitrile copolymer used in the present process tends to bequite stiff, and is prone to bag when mixed on a two-roll rubber mill.The addition of a reactive phenol-formaldehyde resin improves the mixingof the hydrogenated copolymer by reducing the bagging problem.

Thus, the polymer composition is mixed in a conventional manner and thetemperature thereof during mixing is maintained as is known in the art.

In the present process, it is preferred to heat the polymer compositionto form vulcanizates using conventional procedures well known in theart. Preferably, the polymer composition is heated to a temperature inthe range of from about 130° to about 200° C., preferably from about140° to about 190° C., more preferably from about 150° to about 180° C.

Preferably, the heating is conducted for a period of from about 1minutes to about 15 hours, more preferably from about 5 minutes to about30 minutes.

Other conventional compounding ingredients may also be included bymixing with the copolymer in the conventional manner. Such othercompounding ingredients are used for their conventional purposes andinclude activators such as zinc oxide and magnesium oxide; anti-oxidantssuch as diphenyl amines and the like; stearic acid; plasticizers;processing aids; reinforcing agents; fillers; promoters and retarders inamounts well known in the art.

Embodiments of the present invention will be illustrated with referenceto the following Examples which are provided for illustrative purposesand should not be used to limit the scope of the invention.

Further, in the Examples, the following materials were used:

Therban™ XN532A/A4307: a hydrogenated nitrile butadiene polymercommercially available from Bayer Inc.;

Therban™ A4555: a hydrogenated nitrile butadiene polymer commerciallyavailable from Bayer Inc.;

Therban™ A3407: a hydrogenated nitrile butadiene polymer commerciallyavailable from Bayer Inc.;

Therban™ XN533A (A3907): a hydrogenated nitrile butadiene polymercommercially available from Bayer Inc.;

Therban™ XN541C: a nitrile butadiene polymer having a residual doublebond content of 2-4% and commercially available from Bayer Inc.;

Therban™ XO543C/C3467: a nitrile butadiene polymer having a residualdouble bond content of 5.5% and commercially available from Bayer Inc.;

HNBR#1: a hydrogenated nitrile butadiene polymer having a residualdouble bond content of 4%;

HNBR#2: a hydrogenated nitrile butadiene polymer having a residualdouble bond content of 10%;

Rhenogran™ P-50: polycarbodiimide commercially available from RheinChemie;

Dynamar™ L 13890: sodium carbonate commercially available from Dyneon;

Suprapur™ 6395: sodium carbonate (soda ash) commercially available fromEM Industries;

Sodium Stearate: additive;

Stearic Acid NBS: dispersing agent;

Vulkanox™ OCD/SG: antidegradant commercially available from Bayer Inc.;

Vulkanox™ ZMB-2/C5: antidegradant commercially available from BayerInc.;

Vulkacit™ DM/C: benzothiazyl disulfide vulcanizing agent commerciallyavailable from Bayer Inc.;

Vulkacit™ Thiuram MS/C: tetramethyl thiuram monosulfide vulcanizingagent commercially available from Bayer Inc.;

Vulkacit™ Thiuram/C: tetramethyl thiuram disulfide vulcanizing agentcommercially available from Bayer Inc.;

Maglite™ D: magnesium oxide, activator, commercially available from CPHall;

Zinc Oxide: activator;

N660 Carbon Black: filler;

Carbon Black, IRB#6: filler;

Plasthall™ TOTM: plasticizer commercially available from CP Hall;

Spider Sulfur: vulcanizing agent;

DIAK™ #7: triallyl isocyanate, cross-linking activator, commerciallyavailable from E.I. DuPont; and

Vulcup™ 40KE: 2,2′-bis(tert-butylperoxy diisopropylbenzene commerciallyavailable from Hercules.

EXAMPLES 1-4

The following procedure was used for each of Examples 1-4. The polymercomposition used in Examples 1-4 are shown in Table 1. As will beapparent to those of skill in the art, the polymer composition ofExample 1 contains no special additive. Accordingly, Example is providedfor comparison purposes only and is outside the scope of the presentinvention.

The components of the polymer composition were mixed in a Banbury mixerusing conventional techniques. The polymer composition was vulcanized at180° C. for a period of 12 minutes.

The tensile stress at rupture (“tensile strength”) of the vulcanizateswas determined in accordance with ASTM D412-80. Hot air aging propertiesof the vulcanizates were determined in accordance with ASTM-D573-88.Hardness properties were determined using a Type A Shore durometer inaccordance with ASTM-D2240-8 1. The properties of the vulcanizates arereported in Table 2. The hot air aging properties of the vulcanizatesare also illustrated in FIG. 1.

The properties of the vulcanizates reported in Table 2 and illustratedin FIG. 1 clearly illustrate the superiority of the hot air agingcharacteristics of the vulcanizates of Examples 2-4 (special additiveused) when compared to the vulcanizate of Example 1 (conventional MgOadditive used). FIG. 1 is particularly instructive in showing thesignificant improvement in the time needed for the aged vulcanizate toreach 100% elongation at break under the test conditions. Thistranslates into a significant practical advantages in many of theconventional applications of the vulcanizates.

EXAMPLES 5-9

The methodology used in Examples 1-4 was repeated in these Examplesusing the polymer compositions reported in Table 3. As will be apparentto those of skill in the art, the polymer composition of Example 5contains no special additive and the polymer compositions of Examples 6and 7 contain a conventional additive (MgO). Accordingly, Examples 5-7are provided for comparison purposes only and are outside the scope ofthe present invention.

Various physical properties of the vulcanizates were determined asdescribed in Examples 1-4. These properties are reported in Table 4. Thehot air aging properties of the vulcanizates are also illustrated inFIG. 2.

The properties of the vulcanizates reported in Table 4 and illustratedin FIG. 2 clearly illustrate the superiority of the hot air agingcharacteristics of the vulcanizates of Examples 8 and 9 (specialadditive used) when compared to the vulcanizate of Example 5 (noadditive used) and Examples 6 and 7 (conventional MgO additive used).FIG. 2 is particularly instructive in showing the significantimprovement in the time needed for the aged vulcanizate to reach 100%elongation at break under the test conditions. Again, this translatesinto a significant practical advantages in many of the conventionalapplications of the vulcanizates. FIG. 2 is also instructive in showingthat the advantages accruing from using sodium carbonate as a specialadditive: (i) can not be achieved simply by increasing the amount ofconventional additive (MgO), and (ii) are apparent at lower and higherlevels of the special additive.

EXAMPLES 10-14

The methodology used in Examples 5-9 was repeated in these Examplesusing the polymer compositions reported in Table 5. As will be apparentto those of skill in the art, the polymer composition of Example 10contains no special additive and the polymer compositions of Examples 11and 12 contain a conventional additive (MgO). Accordingly, Examples10-12 are provided for comparison purposes only and are outside thescope of the present invention.

Various physical properties of the vulcanizates were determined asdescribed in Examples 1-4. These properties are reported in Table 5. Thehot air aging properties of the the vulcanizates are also illustrated inFIG. 3.

The properties of the vulcanizates reported in Table 5 and illustratedin FIG. 3 clearly illustrate the superiority of the hot air agingcharacteristics of the vulcanizates of Examples 13 and 14 (specialadditive used) when compared to the vulcanizate of Example 10 (noadditive used) and Examples 1 and 12 (conventional MgO additive used).FIG. 3 is particularly instructive in showing the significantimprovement in the time needed for the aged vulcanizate of Examples 13and 14 to reach 100% elongation at break under the test conditions.Again, this translates into a significant practical advantage in many ofthe conventional applications of the vulcanizates. FIG. 3 is alsoinstructive in showing that the trends and advantages discussed abovewith reference to Examples 1-9 are maintained even when a differentnitrile rubber is used.

EXAMPLES 15-22

The methodology used in Examples 5-9 was repeated in these Examplesusing the polymer compositions reported in Table 7. As will be apparentto those of skill in the art, the polymer compositions of Examples 15,17, 19 and 21 contain a conventional additive (MgO). Accordingly,Examples 15, 17, 19 and 21 are provided for comparison purposes only andare outside the scope of the present invention.

Various physical properties of the vulcanizates were determined asdescribed in Examples 1-4. These properties are reported in Table 7. Thehot air aging properties of the vulcanizates of Examples 15-18 areillustrated in FIG. 4 and those of the vulcanizates of Examples 19-22are illustrated in FIG. 5. FIGS. 4 and 5 are particularly instructive inshowing the significant improvement in the time needed for the agedvulcanizate of Examples of 16, 18, 20 and 22 to reach 100% elongation atbreak under the test conditions compared to the aged vulcanizate ofExamples 15, 17, 19 and 21, respectively. Again, this translates into asignificant practical advantage in many of the conventional applicationsof the vulcanizates. FIGS. 4 and 5 are also instructive in showing thatthe trends and advantages discussed above with reference to Examples 1-9are maintained even when a nitrile rubber with a high residual doublebond content is used.

EXAMPLES 23-30

The methodology used in Examples 5-9 was repeated in these Examplesusing the polymer compositions reported in Table 9. As will be apparentto those of skill in the art, the polymer compositions of Examples 23and 26 contain no special additive, Examples 24, 27 and 29 contain aconventional additive (MgO). Accordingly, Examples 23, 24, 26, 27 and 29are provided for comparison purposes only and are outside the scope ofthe present invention.

Various physical properties of the vulcanizates were determined asdescribed in Examples 1-4. These properties are reported in Table 10.The results in Table 10 clearly evidence the significant improvement inhot air aging properties (time needed for the vulcanizate to reach 100%elongation at break under the test conditions) of the vulcanizates madewith the sodium carbonate (Examples 25, 28 and 30) compared tovulcanizates made using a conventional additive (Examples 24, 27 and 29)or with no special additive (Examples 23 and 26). Again, this translatesinto significant practical advantages in many of the conventionalapplications of the vulcanizates.

TABLE 1 Example Ingredient 1 2 3 4 Therban ™ XN532A/A4307 100 100 100100 Rhenogran ™ P-50 — 10 — — Dynamar ™ L 13890 — 3 — Sodium Stearate —— — 2 Vulkanox ™ OCD/SG 1 1 1 1 Vulkanox ™ ZMB-2/C5 0.4 0.4 0.4 0.4Maglite ™ D 2 2 2 2 Zinc Oxide 2 2 2 2 N660 Carbon Black 50 50 50 50Plasthall ™ TOTM 5 5 5 5 DIAK ™ #7 1.5 1.5 1.5 1.5 Vulcup ™ 40KE 6.5 6.56.5 6.5

TABLE 2 Example 1 2 3 4 Compound Mooney Scorch MS LR @ >30 >30 >30 >30125° C. (min.) Unaged Vulcanizate Hardness, Shore A (pts.) 69 69 70 70Ultimate Elongation (%) 255 325 260 280 Vulcanizate Aged For 168 Hours @150° C. Hardness, Shore A (pts.) 80 80 82 80 Ultimate Elongation (%) 205225 240 235 Vulcanizate Aged For 504 Hours @ 150° C. Hardness, Shore A(pts.) 85 85 86 84 Ultimate Elongation (%) 85 145 200 135 VulcanizateAged For 1008 Hours @ 150° C. Hardness, Shore A pts.) 91 86 87 89Ultimate Elongation (%) 15 65 65 40

TABLE 3 Example Ingredient 5 6 7 8 9 Therban ™ XN532A/A4307 100 100 100100 100 Maglite ™ D — 3 6 — — Suprapur ™ 6395 — — — 2.1 4.2 Vulkanox ™OCD/SG 1 1 1 1 1 Vulkanox ™ ZMB-2/C5 0.4 0.4 0.4 0.4 0.4 Zinc Oxide 3 33 3 3 N660 Carbon Black 50 50 50 50 50 Plasthall ™ TOTM 5 5 5 5 5 DIAK ™#7 1.5 1.5 1.5 1.5 1.5 Vulcup ™ 40KE 7.5 7.5 7.5 7.5 7.5

TABLE 4 Example 5 6 7 8 9 Compound Mooney Scorch MSLR >30 >30 >30 >30 >30 @ 125° C. (min.) Unaged Vulcanizate Hardness,Shore A (pts.) 73 71 40 74 72 Ultimate Elongation (%) 250 260 220 220225 Vulcanizate Aged For 72 Hours @ 150° C. Hardness, Shore A (pts.) 7978 77 78 79 Ultimate Elongation (%) 190 205 205 210 185 Vulcanizate AgedFor 168 Hours @ 150° C. Hardness, Shore A (pts.) 81 80 83 83 82 UltimateElongation (%) 125 175 160 195 195 Vulcanizate Aged For 336 Hours @ 150°C. Hardness,Shore A (pts.) 85 81 83 84 84 Ultimate Elongation (%) 80 105110 200 205 Vulcanizate Aged For 504 Hours @ 150° C. Hardness, Shore A(pts.) 86 83 84 86 85 Ultimate Elongation (%) 75 115 115 155 195

TABLE 5 Example Ingredient 10 11 12 13 14 Therban ™ A4555 100 100 100100 100 Maglite ™ D — 3 6 — — Suprapur ™ 6395 — — — 2.1 4.2 Vulkanox ™OCD/SG 1 1 1 1 1 Vulkanox ™ ZMB-2/C5 0.4 0.4 0.4 0.4 0.4 Zinc Oxide 3 33 3 3 N660 Carbon Black 50 50 50 50 50 Plasthall ™ TOTM 5 5 5 5 5 DIAK ™#7 1.5 1.5 1.5 1.5 1.5 Vulcup ™ 40KE 7.5 7.5 7.5 7.5 7.5

TABLE 6 Example 10 11 12 13 14 Compound Mooney Scorch MSLR >30 >30 >30 >30 >30 @ 125° C. (min) Unaged Vulcanizate Hardness,Shore A (pts.) 70 72 72 70 70 Ultimate Elongation (%) 300 205 260 265265 Vulcanizate Aged For 72 Hours @ 150° C. Hardness, Shore A (pts.) 7879 75 76 76 Ultimate Elongation (%) 215 210 225 280 300 Vulcanizate AgedFor 168 Hours @ 150° C. Hardness, Shore A (pts.) 80 80 78 78 81 UltimateElongation (%) 185 190 200 280 255 Vulcanizate Aged For 336 Hours @ 150°C. Hardness, Shore A (pts.) 81 82 83 80 81 Ultimate Elongation (%) 135155 160 290 240 Vulcanizate Aged For 504 Hours @ 150° C. Hardness, ShoreA (pts.) 82 78 84 81 81 Ultimate Elongation (%) 110 140 160 265 285Vulcanizate Aged For 1008 Hours @ 150° C. Hardness, Shore A (pts.) 92 9087 84 85 Ultimate Elongation (%) 15 25 45 210 235 Vulcanizate Aged For1512 Hours @ 150° C. Hardness, Shore A (pts.) 91 96 91 87 84 UltimateElongation (%) 1 2 6 90 145

TABLE 7 Example Ingredient 15 16 17 18 19 20 21 22 Therban ™ XN541C 100100 — — — — — — Therban ™ X0543C — — — — 100 100 — — HNBR#1 — — 100 100— — — — HNBR#2 — — — — — — 100 100 Dynamar ™ L 13890 — 4.2 — 4.2 — 4.2 —4.2 Maglite ™ D 6 — 6 — 6 — 6 — Stearic Acid NBS 1 1 1 1 1 1 1 1Vulkanox ™ OCD/SG 1 1 1 1 1 1 1 1 Vulkanox ™ ZMB-2/C5 0.4 0.4 0.4 0.40.4 0.4 0.4 0.4 Zinc Oxide 2 2 2 2 2 2 2 2 Carbon Black, IRB#6 40 40 4040 40 40 40 40 Spider Sulfur 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Vulkacit ™DM/C 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Vulkacit ™ Thiuram MS/C 0.5 0.5 0.50.5 0.5 0.5 0.5 0.5 Vulkacit ™ Thiuram/C 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

TABLE 8 Example 15 16 17 18 19 20 21 22 Compound Mooney Scorch 9.8 8.627.9 >30 9.1 7.7 10.5 11.5 MS LR @ 125° C. (min.) Unaged VulcanizateHardness, Shore A (pts) 73 73 71 71 71 72 71 72 Ultimate Elongation (%)535 470 730 655 455 400 510 455 Vulcanizate Aged for 72 Hours @ 150° C.Hardness, Shore A (pts) 78 78 77 76 76 76 76 77 Ultimate Elongation (%)470 520 545 640 315 45 305 510 Vulcanizate Aged For 144 Hours @ 150° C.Hardness, Shore A (pts.) 76 73 73 76 76 73 73 74 Ultimate Elongation (%)355 540 480 640 225 455 180 475 Vulcanizate Aged For 216 Hours @ 150° C.Hardness, Shore A (pts.) 82 80 82 80 83 82 86 82 Ultimate Elongation (%)260 480 385 580 125 385 75 275 Vulcanizate Aged For 336 Hours @ 150° C.Hardness, Shore A (pts.) 84 81 82 82 84 83 86 84 Ultimate Elongation (%)205 410 300 550 105 290 55 150 Vulcanizate Aged For 504 Hours @ 150° C.Hardness, Shore A (pts.) 89 85 86 83 90 85 94 88 Ultimate Elongation (%)110 335 155 395 45 120 15 35

TABLE 9 Example Ingredient 23 24 25 26 27 28 29 30 Therban ™ A3407 100100 100 — — — — — Therban ™ TXN532A — — — 100 100 100 — — Therban ™TXN533A (A3997) — — — — — — 100 100 Dynamar ™ L 13890 — — 4.2 — — 4.2 —4.2 Maglite ™ D — 6.0 — — 6.0 — 6.0 — Vulkanox ™ OCD/SG 1 1 1 1 1 1 1 1Vulkanox ™ ZMB-2/C5 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Zinc Oxide 3 3 3 3 33 3 3 Carbon Black, N550 50 50 50 50 50 50 50 50 Plastholl ™ TOTM 5 5 55 5 5 5 5 DIAK ™ #7 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Vulcup ™ 40KE 7.57.5 7.5 7.5 7.5 7.5 7.5 7.5

TABLE 10 Example 23 24 25 26 27 28 29 30 Compound MooneyScorch >30 >30 >30 >30 >30 >30 >30 >30 MS LR @ 125° C. (min.) UnagedVulcanizate Hardness, Shore A (pts.) 73 73 72 73 75 73 73 73 UltimateElongation (%) 255 195 210 275 235 240 235 245 Vulcanizate Aged For 168Hours @ 150° C. Hardness, Shore A (pts.) 82 81 81 84 84 85 83 83Ultimate Elongation (%) 180 190 250 150 160 240 185 260 Vulcanizate AgedFor 504 Hours @ 150° C. Hardness, Shore A (pts.) 86 84 81 89 85 86 86 84Ultimate Elongation (%) 55 85 220 35 70 180 70 260 Vulcanizate Aged For1008 Hours @ 150° C. Hardness, Shore A (pts.) 90 92 83 88 94 89 85 87Ultimate Elongation (%) 15 35 155 5 15 135 25 210 Vulcanizate Aged For1512 Hours @ 150° C. Hardness, Shore A (pts.) 93 96 89 96 95 90 97 90Ultimate Elongation (%) 0 5 140 0 0 85 5 150

What is claimed is:
 1. A vulcanizable composition comprising: (i) anitrile polymer; (ii) a filler; (iii) an additive which is a Group Imetal salt of a carbonate; and (iv) a vulcanization system.
 2. Thevulcanizable composition defined in claim 1, wherein the nitrile polymercomprises a copolymer of a conjugated diene and an unsaturated nitrile.3. The vulcanizable composition defined in claim 2, wherein theconjugated diene is a C₄-C₆ conjugated diene.
 4. The vulcanizablecomposition defined in claim 3, wherein the C₄-C₆ conjugated diene isbutadiene.
 5. The vulcanizable composition defined in claim 2, whereinthe unsaturated nitrile is a C₃-C₅ α,β-unsaturated nitrile selected fromthe group consisting of acrylonitrile, methacrylonitrile,ethacrylonitrile and mixtures thereof.
 6. The vulcanizable compositiondefined in claim 2, wherein the copolymer comprises from about 40 toabout 85 weight percent of the copolymer of bound conjugated diene andfrom about 15 to about 60 weight percent of the copolymer of boundunsaturated nitrile.
 7. The vulcanizable composition defined in claim 2,wherein the nitrile polymer is a copolymer of butadiene andacrylonitrile.
 8. The vulcanizable composition defined in claim 7,wherein the copolymer comprises from about 55 to about 75 weight percentof the copolymer of bound butadiene and from about 25 to about 45 weightpercent of bound acrylonitrile.
 9. The vulcanizable composition definedin claim 2, wherein the copolymer is hydrogenated.
 10. The vulcanizablecomposition defined in claim 9, wherein the copolymer comprises aresidual carbon—carbon double bond unsaturation of less than about 30mole percent.
 11. The vulcanizable composition defined in claim 1,wherein the additive is present in an amount of from about 0.5 to about30 parts by weight per hundred parts by weight of nitrile polymer. 12.The vulcanizable composition defined in claim 1, which further comprisesan additional additive selected from the group consisting of acarbodiimide, a polycarbodiimide and mixtures thereof.
 13. A process forproducing a nitrile polymer vulcanizate comprising the step ofvulcanizing the vulcanizable composition defined in claim
 1. 14. Aprocess for producing a nitrile polymer vulcanizate comprising the stepof vulcanizing the vulcanizable composition defined in claim
 12. 15. Apolymer vulcanizate produced by the process defined in claim
 13. 16. Apolymer vulcanizate produced by the process defined in claim
 14. 17. Amethod for improving the hot air aging characteristics of a nitrilepolymer comprising the step of admixing a nitrile polymer with anadditive which is a Group I metal salt of a carbonate.
 18. The methoddefined in claim 17, wherein the nitrile polymer comprises a copolymerof a conjugated diene and an unsaturated nitrile.
 19. The method definedin claim 17, wherein the nitrile polymer is a copolymer of butadiene andacrylonitrile.
 20. The method defined in claim 19, wherein the nitrilepolymer is hydrogenated.
 21. The method defined in claim 20, wherein thenitrile polymer comprises a residual carbon—carbon double bondunsaturation of less than 30 mole percent.
 22. The method defined inclaim 17, with further comprises an additional additive selected fromthe group consisting of a carbodiimide, a polycarbodiimide and mixturesthereof.